When fabricating electrodes for most H2/O2 fuel cells or sensors, Nafion (DuPont, perfluorinated sulfonic acid polymer) is used as a binder for fixing a catalyst to the electrode surface. Particularly, enzyme electrodes comprising Nafion have been developed in various ways. FIG. 1 is a perspective view of a conventional biofuel cell wherein an anode and a cathode are separated from each other by a proton exchange membrane. A method has been proposed in which the surface of a carbon electrode is coated with Nafion for the dispersion and adsorption of a catalyst and the dispersion of nanostructured materials and an enzyme is attached to the coated Nafion. However, this method entails a problem in that the enzyme is exposed to the external environment so that the enzymatic activity rapidly decreases.
To overcome this problem, a method has been proposed in which an enzyme is entrapped between a carbon electrode and a Nafion membrane by adsorbing the enzyme onto carbon paper, followed by coating with Nafion. However, this method encounters problems in that the enzyme is not uniformly dispersed and it is difficult for the electrons generated in the enzyme electrode by the Nafion membrane to reach directly a current collector.
Accordingly, a method is currently used in which an enzyme is entrapped in a Nafion membrane by immersing carbon paper in a solution mixture of the enzyme and a Nafion solution. This method is advantageous in terms of the dispersion of the enzyme and the stability of the electrode, but involves a problem in that the Nafion reduces the lifespan and activity of the enzyme and interferes with the transfer of the electrons generated in the enzyme electrode to a current collector.